Minigenerator

ABSTRACT

The present invention provides an Electro Surgical Generator (ESG) optimized for lung biopsy. The ESG is exclusively battery operated and fits within the handpiece of modern endoscopic electrosurgical/electrocautery instruments, thereby avoiding wires, adapters, and coupling mechanisms. The ESG is adaptable to generate different waveforms that vary with respect to frequency, pulse width, amplitude, etc. through the use of timing circuits and voltage control (i.e. transformers). The ESG is both energy-efficient and safe. A closed loop feedback system featuring a monitor and controller ensure no more power than necessary is provided to achieve a goal current level. Dynamic Power Control (DPC) and Dynamic Temperature Control (DTC) systems vary power to maintain temperature with the lowest possible power. These features prolong battery life and guard against tissue damage. The generator includes other safety features such as resiliency against and the ability to overcome single fault events such as short circuits.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/148,469, filed Jan. 30, 2009.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to means for powering electrosurgical andelectrocautery tools and instruments. More specifically, the presentinvention relates to cordless battery-powered means for generating powerthat are compact enough to fit within a handpiece, powerful enough foruse in sealing and resecting operations in the lungs, and safe enough toprovide risk reduction incentives over conventional generator systems.Most specifically, the present invention focuses on the aspects of theelectrical circuitry design for the minigenerator system to provideincreased energy efficiency, feedback and alert systems, and adjustableperformance parameters to tailor the procedure to the needs of eachpatient.

2. Description of the Related Art

Battery-operated power generators are desirable forelectrosurgical/electrocautery instruments because they eliminate theneed for wires running from the instrument to generator boxes or walloutlets. This eliminates any chance of a leakage current fault thatcould harm the patient. That makes the unit inherently safe. Inaddition, safety compliance should be easy to obtain by sound electricalcircuitry design that complies with well known and readily availableindustry standards (i.e. IEC 60601 and ISO 14971). With no wires, thesurgeon would be free to articulate the unit without encumbrances,enabling more natural surgical techniques and a greater variety oftechniques.

There have been other attempts to overcome the reliance upon electricalwires and cords in providing electrosurgical/electrocautery tools with areliable power supply. These attempts have confronted the dilemma inthat eliminating the wall outlet electrical power source and relyingcompletely on battery power typically makes the instrument so bulky thatit is no less awkward to use than instruments attached to wires.Alternatively, providing a smaller battery to make the instrument easierto handle may be okay for more refined smaller scale surgical work butcurrent circuitry designs and modes of usage cannot provide the amountof power necessary for more intensive surgeries in larger organs.Accordingly, several designs have accepted wires as necessary for thesupply of a sufficient amount of power. These designs have focused onalternatives that reduce the negative aspects of wires (i.e. the abilityof wires to get in a surgeon's way) rather than eliminating themaltogether. Examples follow.

U.S. Pat. No. 6,039,734 (hereinafter U.S. Pat. No. '734) entitled“Electrosurgical hand-held battery-operated instrument” by Colin CharlesOwen Goble and assigned to Gyrus Medical Limited (Cardiff, GB) disclosesan instrument that is truly without wires. However, it is noted that“[t]his instrument is primarily, but not exclusively, intended for finesurgical work, such as spinal, neurological, plastic,ear-nose-and-throat and dental surgery, and office procedures.” There isno mention of lung, pleural, chest, or thoracic capabilities.Additionally, the instrument uses a single treatment electrode and ismonopolar (see Abstract, claim 1, 1:29-31, etc.). The array of surgicalprocedures compatible with such a design is limited. The minigeneratorof the present invention can be used with bipolar instruments havingmultiple treatment electrodes and this expands the potentialapplications. Since the battery-operated instrument of U.S. Pat. No.'734 is monopolar it requires a return path to be built into the housingof the instrument in order to avoid localizing current in a patient'stissue in the region of a return pad. The return path takes the form ofan electrically conductive shield outside the generator that providescapacitive coupling between the generator and its surroundings (seeAbstract, claims 7-9, 1:38-43, etc.). This built-in return path addssome bulk to the device as the layering is:generator—insulator—conductive shield—insulator. This generator alsouses and provides a conductive path of alternating current (AC) (seeclaim 18). The minigenerator of the present invention can also providedirect current (DC) for electrocautery in which current does not enterthe patient's body. Direct current electrocautery may be safer in somesituations.

U.S. Pat. No. 5,961,514 (hereinafter U.S. Pat. No. '514) entitled“Cordless electrosurgical instrument” by Gary L. Long, et al. andassigned to Ethicon Endo-Surgery, Inc. (Cincinnati, Ohio) achieves a“cordless” electrosurgical instrument in a narrow sense of the term inthat the instrument itself is, in fact, cordless but for power it isrequired to screw-in or plug-in to a trocar adapter unit that has wiresand is itself electrically charged by a wall outlet. The outside of thetubular instrument has electrical contacts that receive energy as theinstrument is passed through a trocar cannula. Thus, the instrument mustbe passed through and in contact with the trocar cannula to receiveenergy and the trocar adapter unit has wires. Connecting the instrumentto the trocar adapter provides an extra step and obligation for asurgeon to perform before beginning to operate. Requiring the instrumentto pass through a trocar cannula limits the angles and directions inwhich an instrument can be manipulated to access and treat a target sitesince it has to pass through the wired trocar adapter first. Thus, theadvances of this system, if any, seem marginal. Typical voltages comingfrom a wall electrical outlet are much higher than the maximum voltagesof reasonably-sized batteries and passing such a high voltage through atrocar cannula adapter unit in proximity to the patient could bedangerous.

U.S. Pat. No. 6,569,163 (hereinafter U.S. Pat. No. '163) entitled“Wireless electrosurgical adapter unit and methods thereof” by CaryHata, et al. and assigned to Quantumcor, Inc. (Irvine, Calif.) improvesupon the wired trocar cannula adapter unit of U.S. Pat. No. '514 byproviding an adapter unit that “contactably couples” to an energy sourceupon direct physical contact by the surgeon (4:30-38). “Contactablecoupling” is defined in the patent as coupling two electrical contactelements by contacting without plugging or connection” (4:27-30).However, the system is not truly wireless in that wires exist, it isjust that they are divided into separate discrete segments, hidden, andinsulated. Wires extend through a surgeon's glove and/or gown toterminate in at least one electrically conductive patch zone (or twopatch zones for bipolar instruments) that provides power to the adapterunit upon direct physical contact. A drawback of this system is that theinstrument itself does not contactably couple to the power supply.Rather, the wireless adapter unit (WAU) stands between the electricalsource in the surgeon's glove or gown and the electrosurgical instrumentto be powered. The instrument itself actually connects to the WAU with acable cord 25 and receptacle 24 (see FIG. 4) or it connects throughwires stripped of their insulation and a spring-loaded plug (5:31-41).It seems it would be a better design to eliminate the adapter unit andcontactably couple the electrical system in the surgeon's glove/gowndirectly with the instrument to be powered. This would streamline theconnections and eliminate the duty to line-up and connect components insitu. This drawback is discussed and compared to the prior art (see5:23-28, 5:31-41, and FIGS. 4A and 4B). U.S. Pat. No. '163 teaches awayfrom a battery pack by suggesting the contactable coupling meansdescribed therein is superior because it doesn't take up space whilebatteries do and can make an instrument bulkier and heavier (2:7-14 and4:36-38).

The minigenerator power system of the present invention overcomes theissues of all of these references by providing a truly wireless systemthat avoids both a separate adapter unit and the need for a couplingmechanism and is capable of being used with bipolar (in addition tomonopolar) instruments. The elimination of a coupling mechanism reducesinstrumentation set-up time and the on-site power generation sourcereduces charging or power-up time. The special handpiece is hermeticallysealed, without any external wires, and with a modern battery havingspecially designed circuitry that minimizes power usage for a lighter,longer-lasting battery-powered instrument.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an electrosurgical/electrocauterygenerator that is completely cordless, free of adapters, and entirelybattery-powered. The generator is compact enough to fit within ahandpiece of an electrosurgical/electrocautery instrument without addingweight or bulk. The generator is designed to fit within the handpiecesof modern, smaller, endoscopic surgical instruments. The batterycomponent of the generator can be as small as contemporary cell phonebatteries (i.e. around 1.5″×1.5″×0.25″).

The cordless nature of the entirely battery-powered generator providessafety improvements for both the patient and healthcare providers(surgeon and operating room staff). There are no cords for anyone totrip over and there is no risk of frayed wires or leaking voltage frompoorly insulated or worn wires. The electric circuitry of the generatorof the present invention has also been specially designed to perform atreduced voltage levels. The system can run off of a battery in the rangeof 6 volts to 24 volts and all voltage levels in the circuitry are low,at battery level, until the very last transformer (see last transformerT2 in FIG. 2 final output diagram). Conventional generators with wiresthat rely on electrical energy from wall outlets typically work with100-250 volts (V) alternating current (AC). Thus, the present designreduces widespread higher voltages.

Other advantages of the cordless battery-powered design of the generatorare that it is much more portable. Physicians working out of severalhospitals, clinics, and out-patient offices (as many do) can carry thesame preferred instrument with them from place to place, therebybuilding skill and confidence from using the same piece of equipment.Generator portability also reduces the need for a separate instrumentand generator at every site or on every floor of a facility, therebyreducing overhead expense which is passed along to maintain lowerprocedure costs for patients and insurance companies. The generatorsystem is so small compared to conventional plug-in wall units it iseven easy to travel with including by plane transportation. Surgeonsshould prefer this cordless battery-powered generator because itdrastically increases their safe range of motion during surgery, givingthem greater ability to “dance” about the operating room andflex/bend/turn as necessary to obtain the best treatment angles withoutworrying about tripping on wires, getting cords tangled, or traversingthe patient with electrically charged cords. Greater instrumentcontrollability results in more precise and accurate cutting (more hit,less miss when aiming at a target) which consequently results in lessbleeding from hitting unintended vessels and other structures. Inaddition to less bleeding, there is less structural damage to unintendedstructures. Better maneuverability also enables improved linear cuttingwith less deviation from a path along a line.

The minigenerator of the present invention is ideal for powering manytypes of electrosurgical/elecrocautery instruments. The minigeneratorcan be used universally with any electrosurgical/electrocautery tools solong as it can fit in the handpiece of the instrument used to powerthose tools. Exemplary tools the minigenerator can be used to powerinclude those with electrodes, optical fibers, barbs, blades, scissors,jaws, tissue-contacting surfaces, vibrators, heaters, ablators,ultrasonic generators, mechanical cutters/corers, spinning cutters, etc.It is especially well-suited for powering instruments that cut and sealtissue, including those that cut and seal through non-mechanical energytransfer means such as radiofrequency ablation, tissue welding,cauterization, infrared lasers, etc.

The electronic circuitry of the generator is arranged in aninterconnected closed loop functional feedback system such that powerdrained from the battery and converted by the converter can be adjustedas necessary to maintain a desired level of current or power supply tothe final output. This internal system can also be connected withanother external component that monitors an external variable, in apatient's body, that is impacted by the final output current or power.For example, a thermocouple might be used to monitor the temperature ofa site in a patient's body. The temperature of a site in contact withthe electrosurgical instrument is influenced by the power provided bythe battery and the current provided to the final output. By providingDynamic Temperature Control (DTC) and Dynamic Power Control (DPC) thepresent invention stabilizes the temperature at an optimal level (orrange) while using the minimum amount of power necessary. Resistance isanother variable that can be measured by a sensor to monitor thecondition of the tissue to ensure it stays within safe ranges whileproviding the best therapeutic benefit.

This feedback system saves energy by providing no more energy than isnecessary to maintain a given level of current or power to the finaloutput or to maintain the value of a variable that measures acharacteristic of tissue in a patient's body at a desired therapeuticlevel. The hydrated condition of live tissues in a patient's body allowsthem to conduct electricity and permits a reduction in power necessaryfor effective treatment compared to desiccated tissues with little or noconduction. However, the extent of hydration and the resistance oftissues changes over the course of treatment and can change abruptly.These changes impact the power requirements to achieve the same effects.Continual feedback provides for the necessary power adjustments tomaintain constant therapeutic benefits and avoid dangerous extremes thatcould cause unwanted outcomes including charring. A moreenergy-efficient instrument also provides an economic benefit byreducing power costs.

According to a preferred embodiment, the generator also includes a meansfor tailoring the frequency, pulse width, and amplitude of the waveformsgenerated to match the needs of each patient and procedure. Timingcircuits in the controller can be used to control the frequency andpulse width while the amplitude is directed by varying the voltage tothe final output stage.

The basic requirements for the circuit are a closed conductive path andan energy source. The battery described herein provides the energysource. The design of the electrosurgical/electrocautery instrument thatconnects the battery to the specific tools and elements it powersprovides the closed conductive path. Other standard circuit elements canbe added to obtain the desired functionality, feedback, controllability,and safety features. These elements include: capacitors, resistors,transistors, transformers, inverters, antennas, diodes, etc. A capacitorstores electric charge. A capacitor is used with a resistor in a timingcircuit. It can also be used as a filter, to block DC signals but passAC signals. A resistor restricts the flow of current, for example tolimit the current passing through a light emitting diode (LED). Aresistor is used with a capacitor in a timing circuit. A transistoramplifies current. It can be used with other components to make anamplifier or switching circuit. A transformer comprises two coils ofwire linked by an iron core. Transformers are used to step up (increase)and step down (decrease) alternating current (AC) voltages. Energy istransferred between the coils by the magnetic field in the core andthere is no electrical connection between the coils. An inverter canhave only one input and the output is the inverse (opposite) of theinput (i.e. the output is true when the input is false). An inverter isalso called a “NOT gate”. An antenna receives and transmits signals,typically radiofrequency (RF) signals. A diode is a device which onlyallows current to flow in one direction.

Advantages of the invention will be set forth in the description anddrawings which follow, and in part will be obvious and implied from thedescription and drawings, or may be learned by practice of theinvention. Advantages of the invention may be realized and obtained bymeans of the instrumentalities and combinations particularly pointed outhereinafter and any other means suggested by them.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 shows a block diagram illustrating the basic feedback loop of thecircuitry and showing how the current monitor and controller worktogether to adjust the amount of energy drained from the battery and/orprocessed by the converter and provided to the final output.

FIG. 2 shows a circuit diagram demonstrating the final output and howthis is fed by and isolated from the power generation components andremaining circuitry.

FIG. 3 shows a power monitor that is used to sample the current bydeveloping a voltage drop across a small resistance of 0.1 ohm. Thevoltage is numerically equal to the amperage drawn by the final outputstage divided by 10. The voltage value is fed to the controller todetermine if it is within an acceptable range.

FIG. 4 shows a simple analog version of a timing circuit inside thecontroller used to generate the frequency and pulse width.

DETAILED DESCRIPTION OF THE INVENTION

The design has been optimized for safe, energy-efficient batteryoperation. All voltage levels in the circuitry are low, at batterylevel, until the very last transformer T2 (see the final output diagramshown in FIG. 2 illustrating how the last transformer T2 is isolated).The last transformer multiplies the voltage and isolates the patientfrom the entire circuit. The output stage is simple, but efficient,ideal for battery operation. The use of a “swinging choke” T1 (see FIG.2) provides the necessary positive and negative outputs by using onlytwo Field Effect Transistors (FETs).

Using a wide range input DC-to-DC converter design, the latest batterytechnology can be utilized. Any battery input from about 6 volts up to24 volts can be accommodated. The output of the DC-to-DC converter doesnot vary with changes in the input. Therefore the unit can provide anenergy output (i.e. radiofrequency or RF output) that is independent ofbattery voltage. This fixed output feature makes battery lifedeterministic and predictable. A radiofrequency output is listed asexemplary only and is not limiting. The generator of the presentinvention could also be used in the handpiece of instruments thatproduce other energy forms as outputs, including infrared (IR),ultraviolet (UV), ultrasonic, lasers, etc.

A battery can be selected to easily provide enough power for theprocedure, plus a large safety factor, and still fit comfortably in thehandle of an electrosurgical/elecrocautery instrument. Typical powerrequirements for a lung biopsy are 30 watts for 30 seconds. Using two12-volt batteries with only 50% conversion efficiency, the batterycapacity requirement would be 0.04 Amp-Hr:

$\begin{matrix}{{{30\mspace{14mu} W} = {12\mspace{14mu}{V@2.5}\mspace{14mu} A}},{2.5\mspace{14mu} A \times 0.5\mspace{14mu}\min \times {Hr}\text{/}60\mspace{14mu}\min \times 2\left( {50\%\mspace{14mu}{efficiency}} \right)}} \\{= {0.04\mspace{14mu}{Amp}\text{-}{{Hr}.}}}\end{matrix}$

Small lithium-ion batteries in a portable form factor typically provide0.5 Amp-Hr.

This provides an excess capacity of greater than ten times (10×):0.5/0.04=12.5.

Monitoring the power supplied to the final amplifier stage and notsupplying power if a momentary short circuit occurs, as happens in theseprocedures, extends battery life. During a short circuit the powerrequired theoretically becomes infinite and battery life would bejeopardized if it were not detected. According to a preferredembodiment, the current to the final amplifier (final output) ismonitored. This current is directly proportional to the amount of power(i.e. radiofrequency power) being supplied to the tissue. If a shortoccurs, the current detector will command the controller to cut thepower, wait for a moment, then reapply a small amount of power todetermine if the short has been cleared. If it has been cleared, thenthe full procedural power is restored. Alarms in the form of an audiblesound (i.e. a beep or different pitches and tones), lights (includingcolored or flashing), and/or vibration (or another tactilely sensedchange) are provided if a short circuit occurs so that the surgeon isimmediately aware.

The power monitor samples the current by developing a voltage dropacross a small resistance of 0.1 ohm. This voltage is numerically equalto the amperage drawn by the final output stage and divided by 10. Thevoltage is fed to the controller to determine if it is in an acceptablerange. Due to their interrelationship, if the voltage is in theacceptable range the current (amperage) is also in the acceptable range.

The frequency, pulse width, and amplitude of the energy output (mostcommonly RF output for energy in the radiofrequency range) to thepatient are all adjustable in real time. Handpiece and/or foot treadlecontrols can be provided so that the surgeon can adjust these parameterseasily on-the-spot without interrupting cutting/resecting or sealing oftissue. Then, there is no need to stop, walk to a main console andmanipulate controls there. Optionally, a programmer may also beincorporated and used when a particular waveform pattern is desired thatcan be too complicated or exhausting to achieve by manual operation(handpiece control buttons or foot treadle) alone. The ability to adjustthe waveform characteristics allows the unit to produce the mosteffective waveform for each particular procedure. Different procedures,different instruments, different patients, and different sites on thesame patient have different needs with respect to waveforms. Thegenerator of the present invention is designed to accommodate all ofthese needs to achieve better surgical results with shorter proceduresand longer battery life.

The frequency and pulse width are generated with timing circuits in thecontroller. The controller communicates with the current monitor andthese variables can be adjusted, if desired, in response to changes inthe current. The timing circuits can be analog or microprocessorcircuits. A simple analog version of a proven circuit is shown in FIG.4.

The amplitude is a function of the voltage to the final output stage.That voltage is determined by the set point on the DC-to-DC converter,which is, in turn, provided by the controller. As shown in FIG. 1, thecontroller communicates with the converter, the current monitor, and thefinal output to ensure the optimum voltage is provided to the finaloutput from the converter. As previously stated, this voltage passedalong to the final output is not dependent upon the voltage of thespecific battery selected to power the generator. The voltage to thefinal output can be set at a specific value and that value can beachieved with any battery used by the generator.

Additional sensors can be provided near a distal tip of theelectrosurgical/electrocautery instrument powered by the generator at atarget site in a patient's body to measure these variables (frequency,pulse width, amplitude) to ensure the goal values are achieved and todetect the numerical values at which the best performance occurs.Performance can be felt by the surgeon manipulating the instrument, seenon a monitor for endoscopic procedures, or seen with direct vision foropen procedures.

By utilizing temperature feedback (Dynamic Temperature Control or DTC)which can be determined from a thermocouple at the tissue site, powercan be dynamically varied (Dynamic Power Control or DPC) during theprocedure. It is possible to start the procedure at full power, monitorthe temperature of the tissue, and reduce the power as soon as thetemperature starts to approach the therapeutic temperature. A closedloop controller would provide just enough power to maintain the desiredtemperature and thereby maximize battery life. For example, temperatureranges of 60-75° C. in tissue have been shown to be optimal for cuttingand sealing procedures (see Massachusetts Institute of Technology'sTechnology Review of Nov. 19, 2008: “Healing with Laser Heat—Surgicallasers could soon heal cuts as well as make incisions” by LaurenGravitz.)

The circuitry of the system can vary among the different embodiments solong as the objective is satisfied: energy conservation while providinga desired effect on target tissue that dynamically responds to thechanging state of tissue as it is heated. Accordingly, the effect ontissue can be made to approach a known optimal range as measured by oneor more tissue characteristics including resistance, temperature,density, moisture content, etc. In some cases the desired effect isassured by maintaining constant temperature of the tissue as energy istransferred to it. As the material nature of the tissue changes as it isheated, the amount of energy supplied to the tissue to maintain theoptimal temperature may change. Temperature measures the degree of heatin the tissue and an average kinetic energy of particles in the tissue.

According to a preferred embodiment, the circuitry comprises at leastone capacitor and at least one resistor. More preferably, there arethree capacitors and two resistors with a resistance of at least oneresistor between 0.05 and 0.15 ohms. According to a preferredembodiment, there is a transformer that is a swinging choke transformerand there are two field effect transistors (FETs), such that theswinging choke transformer provides both a positive and a negativeoutput, as necessary, by using only the two field effect transistors(FETs).

As for the power source and converter, preferably, the battery has avoltage from 6 volts up to 24 volts and the energy converter is capableof handling DC-to-DC (direct current to direct current) conversion.

The controller preferably includes at least one timing circuit. Thetiming circuit may be an analog or a microprocessor circuit anddesirably has at least one inverter or NOT gate. To provide a desiredeffect on tissue the final output preferably operates at 30 watts ormore for 30 seconds or longer.

The exact power level provided by the final output to tissue and thelength of time it is provided over to produce the desired effect willdepend upon the details of a particular patient. Feedback sensors insitu ensure the system is properly calibrated for each individualpatient and that the appropriate amount of energy is transferred to thetissue to produce a desired sealing or resecting effect withoutcharring, burning, etc. Independent feedback sensors of one or moretypes (including those that measure temperature, resistance, moisturecontent, etc.) can be positioned in a patient at a tissue site to whichan electrosurgical/electrocautery instrument (powered by theminigenerator herein) is applied and these sensors can be connected todirectly or wirelessly communicate with the controller of theminigenerator. In some cases the sensors are part of the distal end ofthe electrosurgical or electrocautery instrument with which theminigenerator is used while in other cases they are independentcomponents separately embedded in the tissue.

Next, a general procedure for the collection of biopsy samples from alung is outlined. The generator of the present invention could be usedto power the electrosurgical instruments used to perform the biopsyprocedure. However, this is just one application and is not intended tobe limiting. The generator also can be used after biopsy to power moreintensive treatment procedures with the objective of removingsubstantial quantities of tissue (much larger than the sizes needed forbiopsy analysis) and sealing large regions (i.e. to reduce the spread ofcancer or other disease, redirect flow, and/or prevent fluidaccumulation or leakage).

Although there is an emphasis on the lung, the generator is not limitedto powering procedures within the lung. One having ordinary skill in theart will recognize that the generator and methods described herein arereadily adapted for the collection of biopsy samples, sealing (as asubstitute for threaded sutures), and cutting/resecting operations inseveral regions of the body including nerve repair, blood vessel repair,cornea transplants, etc.

General Procedure

Step One: Consent, Anesthesia, Medical Staff, and Set-Up

Prior to beginning the procedure, the informed consent of the patientshould be obtained.

One advantage of the present invention, as compared to traditionalopen-surgery biopsy techniques, is that it is done under localanesthesia rather than general anesthesia. Consequently, there is lessinterference with the homeostasis of bodily functions and recovery timeis reduced permitting patients to avoid lengthy and expensivepost-operative stays in the hospital recovery unit. Further, localanesthesia generally allows for a quicker post-operative assessment ofthe patient's condition and of the success of the procedure. Thepreferred drug of choice for local anesthesia in the present procedureis a long-acting local anesthetic agent like bupivacaine. Lidocaine,novacaine, ropivacaine and procaine may also be used. Intravenoussedatives including versed, morphine, fentanyl and other agents enhancethe effects of the local anesthetic agent by causing the patient tobecome sleepier, less anxious, and number to sensations like pain. Ananesthesiologist or anesthetist should be required to standby during thebiopsy procedure until the operating physician is very comfortable inusing the devices described herein.

This procedure is to be done in a procedure room, operative room, or inthe ICU (Intensive Care Unit). A RN (Registered Nurse) should bepositioned bedside throughout the procedure and sterile precautionsshould be used. A telemetry unit should be used to monitor heart rateand blood pressure as needed. Oxygen saturation should also be measuredthroughout the procedure.

Typical endoscopes provide channels for gas and fluid exchange betweenthe external environment and the internal biopsy site. Carbon dioxide oran equivalent gas may be insufflated to the biopsy site through such achannel, during the biopsy procedure, at flow rates of 2-4 liters perminute. Carbon dioxide gas is preferable because it is non-combustible(unlike oxygen), dissolves in blood, and does not cause clots or bubbleswhen introduced into the rib-restricted thoracic cavity (unlike air).Any other gas having these same advantageous characteristics that isotherwise medically compliant and safe for introduction within theinterior of the thoracic cavity may also be used.

The patient's diagnostic data is to be reviewed by a pulmonologist. Itis preferable to have CXR (Chest X-Ray) and CT (Computed Tomography)scans readily available. Preferably, a thoracic surgeon on standbyshould be available for back-up support and assistance.

Step Two: Incision, Insertion of Minithoracoscope, and Insufflation toInduce Pneumothorax

The point of entry is based on the diagnostic data as determined by thepulmonologist. Once the point of entry is determined, the operative sitesurrounding the point of entry is prepared and draped in a sterilemanner.

Next, the local anesthetic agent is infiltrated. A total of 5 mL isusually adequate to anesthetize from the skin to the pleura. A needle isinserted into the intrapleural space. An ease in injection is noted asthe needle tip enters the pleural space. This can be confirmed byaspirating air.

A blade knife (size: 11-gauge) is used to make an incision(approximately 2 mm). This incision will facilitate the entry of theChest Innovations (trademark) (hereinafter, CI) minithoracoscope(trademark). The entry point is always superior to the rib to preventinjury to the intercostal vessels. The CI minithoracoscope has amulti-port minitrocar (trademark) that is held in the midportion of thescope for better directional control. Steady forward pressure is neededto enter the pleural space. Insufflating the internal region during theintroduction of the minithoracoscope (or other instruments) is preferredto reduce the possibility of lung injury. Providing continuousinsufflation to the internal region of the site to be biopsied alsofacilitates visualization and prevents fogging of the CIminithoracoscope.

As the pleural space is entered, there is a “give” or sudden drop inpressure, at which time the multi-port minitrocar is removed. Carbondioxide insufflation continues into the intrapleural space at 2 litersper minute following the removal of the multi-port minitrocar to inducea pneumothorax causing the lung to collapse. When the lung is collapsed,it is easier to visualize, grasp, and manipulate for obtaining a biopsy.It is also easier to reach a greater number of target locations forsampling from a single incision site when the lung is collapsed. Duringthe procedure the intrapleural pressure is maintained at less than 8mmHg. The anesthesiologist or anesthetist keeps a watch over the bloodpressure as excessive carbon dioxide insufflation may cause hypotension,such as from a mediastinal shift as pressure changes in the thoraciccavity push the heart over. In the event of hypotension, the situationcan easily be corrected by stopping the flow of carbon dioxide andaspirating the port. Accordingly, it is important to use a low flow rateof carbon dioxide throughout the procedure to avoid rapid fluctuationsin blood pressure and intrapleural pressure.

Step Three: Insertion of Camera and Instruments

As an alternative to relying solely upon the tactile sensation of apressure drop to determine when the pleural space has been entered, asecond option is to introduce a CI minithoracoscope with a camera in oneof its ports so that insertion of the biopsy needle and insufflation ofcarbon dioxide are under direct vision. Using this option, the CIminicamera (trademark) is inserted through a port of theminithoracoscope. The location of the CI minithoracoscope within theinterior of a patient can be confirmed by visual inspection of theexternal monitor which receives image signals transmitted by theminicamera. The monitor is usually available with most scope towers. TheCI minicamera may need to be defogged occasionally throughout theprocedure. Outside of the body, a solution such as “Fred” by Dexide,Inc. or “Dr. Fog” by O.R. Concepts, Inc. (see also U.S. Pat. No.5,382,297 assigned to Merocel Corporation) can be used to defog theminicamera. Inside of the body, directing the source of carbon dioxideinsufflation at the lens of the minicamera may assist to defog.

As the minithoracoscope advances internally through the prospectivebiopsy region, the pathology is identified and reviewed. Pictures aretaken by the minicamera for documentation and correlation with biopsysamples.

Once a target biopsy region is identified based on the imagestransmitted by the minicamera, the working miniport (trademark) of theminithoracoscope is ready to be used. The miniport is an instrumentchannel or a fluid/gas exchange channel. The CI mininstruments(trademark), including forceps, staplers, and energy-transferringsealing and separating devices are inserted to obtain biopsy specimens.The specimens are then removed for pathology analysis and/or for cultureand sensitivity studies. If bleeding is encountered during the internalmanipulation of CI mininstruments, CI minicoagulators (trademark) can beused to promptly control bleeding. Further, CI suction devices areavailable for aspiration of pleural fluid. Other solutions can also beprovided through one of the working miniports of the minithoracoscopeand suctioned out after they are utilized. For example, a salineirrigation solution can be introduced to prevent clots. Electrolyticsolutions, cooling fluids, cryogenic fluids, chemotherapeutic agents,medicaments, gene therapy agents, contrast agents, and infusion mediamay also be used. (See U.S. Pat. No. 6,770,070 assigned to R. ITAMedical Systems, Inc. at col. 10, lines 14-17.) Cooling fluids may beprovided to ensure the temperatures of energy transfer elements (onsealing and separating instruments) stay within a safe range. Cleaningsolutions may be provided to ensure the surface of energy transferelements stays free of materials such as loose tissue particles orcharred tissue.

Step Four: Removal of the Minithoracoscope and Optional Insertion of CIKink-Less, Non-Buckling Chest Tube, if Necessary

Once the internal inspection and sampling procedure is complete, a guidewire is introduced through the working miniport of the minithoracoscopeand placed in a desired location. The CI minithoracoscope is thenremoved.

In many cases, once the CI minithoracoscope is removed, the procedure iscomplete and a chest tube need not be provided. For example, when the CImininstruments used to obtain biopsy samples seal the site from whichthe sample is collected (prior to, simultaneously with, or shortly afterseparating the desired sample from the surrounding tissue), internalbleeding and drainage can be entirely avoided or at least substantiallyreduced. Use of the rapid tissue sealing and separating capabilities ofmodern technologies (including those that rely upon heat to both sealand separate) coupled with the small scale of the sampling instrumentsdescribed herein has the advantage of avoiding the need for a chest tubein many cases.

Chest tubes are generally provided to compensate for incomplete sealingat the biopsy site during incision and sampling. Thus, a chest tubepermits the drainage of blood, gases, and internal fluids over anextended period of time, as the biopsied site heals.

If a chest tube is found to be necessary, CI minidilators (trademark)are inserted first, along the tract the tube is to follow in order toenlarge the tract. A Seldinger technique can be used to position thechest tube. A single skin stitch can be used to secure the chest tube inposition. Alternatively, other methods of securing the chest tube can beused if the stitch needs to be avoided.

Once the chest tube is properly in place within the interior of thepatient, it is connected to a chest drainage system and 20 cm of suctionis applied. A post-operative chest X-Ray should be obtained in theimmediate post-operative period while the chest tube is in place.

Although any chest tube may be used with the methods of this invention,preferably the CI chest tube is used if a chest tube is determined to benecessary. The CI chest tube is highly desirable as compared withconventional chest tubes because, unlike most flexible chest tubes, itdoes not kink and does not buckle. Unlike most rigid chest tubes, the CIchest tube is not painful.

The CI chest tube comprises a long, hollow, tubular member with an outercore that is softer than the inner core. The softer outer core minimizesa patient's sensation of pain upon contact of the tube's externalperiphery with the surrounding bodily environment in which the tube isinserted. The more rigid structural integrity of the inner coreminimizes the chance that the tube will buckle (blocking flow) uponbending as it is maneuvered internally. Within the walls of the tube'sinternal lumen is a deployable elastic element that can be activatedfrom a proximal control site to remove kinks as they emerge, if theyemerge. The internally deployable elastic element replaces theconventional trocar insertion method for removing tubular kinks.

Step Five: Removal of Optional Chest Tube

Chest tube removal is at the discretion of the pulmonologist. A band-aidmay be applied after the chest tube is removed to protect the insertionarea.

A minigenerator as described herein could be used to power theinstrument used in the above biopsy procedure.

The present invention is not limited to the embodiments described above.Various changes and modifications can, of course, be made, withoutdeparting from the scope and spirit of the present invention.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A generator, comprising: a feedback circuit,including: a battery; an energy converter; a controller circuit; anoutput circuit configured to provide an output signal; and a monitorcircuit configured to sample a current provided to the output circuit bysensing a voltage across a resistance in the range of 0.05 and 0.15ohms, the monitor circuit being configured to provide said voltage tothe controller circuit, wherein the controller so that the controllercircuit is configured to adjust an amount of energy provided by theenergy converter to the output circuit such that said voltage ismaintained at a value numerically equal to the current provided to theoutput circuit divided by
 10. 2. The generator of claim 1, wherein thefeedback circuit is configured to maximize energy conservation or tominimize energy drained from the battery while maintaining a giveneffect provided by the output circuit on an external element, byproviding a minimum amount of energy necessary to obtain the effect,wherein the minimum amount of energy necessary to obtain the effectvaries with time.
 3. The generator of claim 1, wherein the feedbackcircuit further comprises a transformer and wherein all voltage levelsin the circuitry are low, at battery level, until a last transformerbefore the final output.
 4. The generator of claim 3, wherein thefeedback circuit further comprises a capacitor and a resistor.
 5. Thegenerator of claim 3, where the feedback circuit further comprises atleast two field effect transistors.
 6. The generator of claim 3, whereinthe transformer is a swinging choke transformer.
 7. The generator ofclaim 4, wherein the feedback circuit further comprises at least oneadditional element selected from the group consisting of: a diode, anantenna, and an amplifier.
 8. The generator of claim 2, wherein anenergy output of the energy converter is constant throughout changes inenergy input to the converter.
 9. The generator of claim 1, wherein theoutput signal is a radiofrequency signal.
 10. The generator of claim 9,wherein the feedback circuit is configured to vary a value of currentsupplied to the output circuit and an amount of radiofrequency energybeing supplied to a tissue while maintaining a constant value for avariable that measures a characteristic of the tissue.
 11. The generatorof claim 10, wherein the feedback circuit is further configured to varyan amount of power supplied by the battery while maintaining a constantvalue for a variable that measures a characteristic of the tissue. 12.The generator of claim 1, wherein the monitor circuit is configured todetect a short circuit.
 13. The generator of claim 1, wherein thecontroller is configured to adjust each of a frequency, a pulse width,and an amplitude of the output signal in real time.
 14. The generator ofclaim 1, wherein the controller comprises a timing circuit.
 15. Thegenerator of claim 14, wherein the controller has an output signal thetiming circuit of the controller being configured to generate the outputsignal of the controller, the output signal having a frequency and apulse width.